Power recovery damping system



June 5, 1951 A. A. BARCO 2,555,828

POWER RECOVERY DAMPING SYSTEM Filed Dec. 1, 1948 INVENTOR Allen jfiarcaPatented June 5, '1951 UNITED STATES OFFICE POWER RECOVERY DAMPINGSYSTEM Allen A. Barco, Jackson Heights, N. Y., assignor to RadioCorporation of America, a corporation of Delaware 16 Claims.

erably due to the energy dissipated in the damping circuits, this energynot being gainfully utilized. In early television practice theelectromagnetic deflection systems suffered considerable losses in thisrespect, which in turn stimulated subsequent development of powerrecovery systems in which some of the stored electromagnetic reactiveenergy normally dissipate-d in the damping system is capacitively storedand employed to effect a boost in B supply voltage applied to the vacuumtube driving the deflection system. Such power recovery or powerfeedback system has greatly improved the operating efiicienciesobtainable in deflection systems as a whole. However, most prior artsystems of this kind require the utilization of a step-down transformerin order to realize reactive damping currents of proper magnitude toreadily permit power feedback into the B supply circuit of the drivingvacuum tube. The use of a transformer in this connection of courserepresents certain additional costs in circuit construction as well asintroducing inherent losses in the system due to leakage reactance andmagnetichysterisis. The losses incurred through use of a transformer forcoupling energy from the plate circuit of the defiection driving tube tothe damped deflection yoke of course may-be obviated by direct inclusionof the yoke in the anode circuit of the vacuum tube. However, such adirect connection has not been regarded as one readily lending itself topower recovery operation.

Furthermore in television receiver applications, the direct drivearrangement for the deflection yoke has in the past displayed anotherawkward feature, that being the diificulty of obtaining from thedeflection system an economical form of pulse set-up power supply fordevelopment of an accelerating potential for the associated cathode rayreproducing device. In a co-pending application by Simeon I. Tourshouand William E. Scull, Jr., Serial No. 56,562 filed October 26, 1948 2entitled High Voltage Power Supply this latter difiiculty has beenovercome in part through the application of an autotransiormer havingits primary connected in series with the deflection yoke circuit andsubsequently rectifying the high voltage positive pulses so obtained toproduce the appropriate high unidirectional accelerating potential. Theinclusion of this autotransformer primary in the yoke circuit does,however, reduce to a considerable extent the unidirectional voltageactually applied to the anode of the output tube and consequently asomewhat higher B+ power supply potential is normally required tocorrect for this voltage drop. This provision of such an increase inpotential represents considerableadditional cost in the design of thetele vision receiver power supply.

The present invention contemplates the realization of a power recoverysystem associated with an electromagnetic deflection system wherein thedeflection yoke is directly included in the plate circuit of the drivingvacuum tube. By capacitively coupling separate sections of thedeflection coil and applying separate damping to each of said sections,there is then developed across the capacitance involved a B-boostvoltage which results from recovery of the reactive energy cyclicallystored in the deflection yoke sections.

It is therefore a purpose of the present invention to provide animproved form of power recovery damping system for electrical circuits.

It is another purpose of the present invention to provide an improvedform of deflection circuit for television systems wherein a portion ofthe damped cyclically reactive energy in the yoke circuit is applied foreiiectively boosting the available polarizing potential of the drivingvacuum tube.

Still another object of the present invention resides in the provisionof a novel form of power recovery system particularly applicable todirectly driven electromagnetic deflection coils in television systemswhereinthe deflection coils are included in the series with theanode-cathode circuit of the deflection system driving vacuum tube.

It is another purpose of the present invention to provide a simple andnovel electrical damping arrangement which provides power feedbackoperation of a plurality of capacitively coupled inductance elementsconnected in series across a signal voltage.

The present invention has numerous other objects and features ofadvantage, some of which, together with the foregoing, will be set forthin the following description of specific apparatus embodying andutilizing the inventions novel method. It is therefore to be understoodthat the present invention is not limited in any way to the apparatusshown in the specific embodiments as other advantageous applications inac cord with the present invention, as set forth in the appended claims,will occur to those skilled in the art after having benefited from theteachings of the following description especially when considered inconnection with the accompanying drawings in which;

Figure 1 shows one form of the present invention as applied to a typicaldirect-driven television deflection system.

Figure 2 shows another embodiment of the present invention as applied toa transformer coupled television deflection system.

Referring now to Figure 1, there is shown a portion of a typicaltelevision deflection system. Here synchronizing pulses are applied atterminal iii to synchronize the operation of deflection signal generatori2 which in turn produces a typical deflection sawtooth waveform, suchas I 4. The signal I4 is then applied to grid is of cathode followervacuum tube l8. The anode 2B of vacuum tube !8 accordingly is connectedthrough a dropping resistor 22 to a source 24 of anode polarizingpotential. The condenser 26 establishes the anode at substantially A. 0.ground potential. A suitable cathode follower resistance 28 is connectedin the cathode to ground circuit of the vacuum tube 18 so as to providea low impedance driving source for the grid 30 of output vacuum tube 32.A suitable negative operating bias is achieved for the grid 39 byinclusion of resistor 34 in the cathode ground circuit of vacuum tube32. Rheostat 36, connected from a source of positive potential 38 to thetop of resistor 34, allows the voltage drop across resistor 34 to besufficiently in excess of the D. C. voltage drop across cathode followerresistor 28 to establish proper negative grid biasing of the tube 32.The cathode by-pass condenser 49 may be provided to reduce signaldegeneration in the cathode circuit of the output tube. The screen grid32 is conveniently supplied with a positive polarizing potential throughresistor 44 connected with terminal 46 of a positive source ofpotential. The screen A2 is in turn held in substantially A. C. groundpotential by means of by-pass capacitor 48.

The anode 50 of the output vacuum tube 32 is then connected through theprimary winding 52 of autotransformer 54, through the first section 56of the deflection coil XX, through resistor 58 and then through thesecond section 69 of the deflection coil XX to a source of positivepolarizing potential having a terminal at 62. In shunt with resistor 58is a storage capacitor 64 across which is to be developed (ashereinafter described) the B-boost or recovery voltage for the system.Damping diode 65 with its anode 68 connected with one terminal ofcapacitor 64 in effect provides damping for the first section 56 of thedeflection coil XX. correspondingly, damping diode '10 with its anode I2connected with the source of positive polarizing potential 52 and itscathode 74 connected with the other terminal of capacitor G4,effectively provides damping for the second section 60 of the deflectioncoil XX. In practice deflection coil XX may correspond to the usualZ-section horizontal or vertical deflection winding of a televisiondeflection yoke designed for direct drive by inclusion in 4 the anodecircuit of the deflection signal output tube.

As is shown. a novel form of high voltage power supply for theaccelerating anode T8 of the kinescope I6 is provided through the use ofautotransformer 54. This form of high voltage power supply for use inconnection with deflection systerns having the deflection yoke directlyconnected in the anode-cathode circuit of the driven Y vacuum tube isdisclosed in a co-pending appli- I cation by Simeon I. Tourshou et al.,supra. As

more fully described in the related specification, the deflectioncurrent for the yoke winding XX passes through the primary 52 of theautotransformer 54 and therefore induces in the secondary 53 highvoltage positive pulses corresponding in time to the kickback pulses 5|occurring on the plate 50 of vacuum tube 32. These high volt age pulsesare then rectified by the diode to develop a high unidirectionalpotential across capacitor 32. The voltage appearing thereacross'is thenfiltered through filter resistor 84 and ap plied to acceleratingterminal I8 of cathode ray tube 56. An auxiliary winding 85 on thetransformer 54 supplies heater power for the filament 88 of the highvoltage rectifier 80. 5

In the operation of the recovery circuit of Figure 1, the damping diodes66 and T0 operate in accordance with conventional reaction scanning typeof deflection system operation as related to the individual sections ofthe deflection winding with which they are respectively associated.Accordingly, the first part of deflection scanning cycle (which will behere considered as due to the reaction scanning action of the individualdamping systems) is provided by energy stored in the respectiveinductances 56 and 69 .at the end of retrace phase of the deflectioncycle. As is well known to those skilled in the television art,immediately following the retrace or return phase of the deflectioncycle, at which time there is zero current through the vacuum tube 32,the dir' odes 65 and H3 will become conductive to. establish a reversedcurrent flow through thegrespective winding sections as the result ofthe stored magnetic energy in these coil sections. For instance, in thecase of the diode 66, immediately following retrace, the diode 66 willbecome conductive to pass a damping current Id in the direction of thearrow 90. This passage of current in the direction indicated, ineffect'adds energy to the capacitance 64 thereby making the terminal 92thereof more positive than itscorresponding terminal 94.correspondingly; the damping current through diode 18, associated withthe second portion 52 of the yoke winding XX, is in the direction of thearrow 96 and can be seen to further add energy to the capacitor 64during its flow in such a direction to cause the terminal 82 to becomepositive with respect to the terminal 94. It is clear that the dampingcurrents through the respective diodes B6" and 1B occur simultaneouslyso that as faras the yoke XX is concerned, a conventional reactionscanning damping arrangement has been provided, the respective dampingcurrents through the diodes in practice being substantially equal.

Investigation of the circuit arrangement will show, however, that thecapacitor 64 is in fact in series between the positive B supply terminalat 62 and the anode 50 of vacuum tube 32, so that any voltage developedacross capacitor 54 is additively combined with the positive B supply.Thus, damped reactive energy is stored by capacitor 64 during thereaction scanning cycle and made of the deflection cycle.

ready for use by the tube 32 during the ensuing driven phase of thedeflection cycle.

It will be found in practice that the sum of the two equal clampincurrents through the diodes 66 and I will, to a close approximation, beequal to the average plate current required during the driven phase ofthe deflection cycle. Hence, the capacitor 64 will maintain anapproximately steady unidirectional potential which represents a boostvoltage for the system.

The value of the capacitor 60 should be large enough so that during thedriven phase of the deflection cycle in which the vacuum tube 32 isrendered conductive, the plate current energy requirements of the vacuumtube will not be sufficient to appreciably alter the potential acrossthecapacitor 64. This, of course, would produce distortion in the latterportion of the driven phase Variable resistor 58 is shown in shunt withthe capacitor 54 in order to provide a convenient control of thewaveform of resulting deflection signal through the coil sections 56 and60. This resistance 58, although not necessarily employed, may assumevalues of from five to ten thousand ohms and functions as a variablesize and linearity control over the resulting television function.

' As explained in connection with Figure 1, the deflection yoke windingXX is in effect directly connected or direct-coupled to the outputvacuum tube 32 by inclusion of the winding sections 56 and B0 in theanode-cathode circuit of the output tube. Advantages of the presentinvention, however, although finding particularly useful application insuch direct-coupled systems, also may be enjoyed in combination withtransformer coupled systems. Such an arrangement is shown in Figure 2 ofthe drawings. Here the anodecathode circuit of the vacuum tube 32includes the primary Winding 08 of coupled transformer I00, such thatdeflection signal energy is made available across the transformersecondary I02 for activation of the damped deflection system embracingy'oke winding sections 58 and 00 of the deflection winding X-X.Inspection of the damping arrangement of the deflection coil windingsections 56 and 00 by damping tubes I04 and I06 will show that thecircuit configuration is substantially the same as that shown in Figure1-.

The only difference in the transformer coupled arrangement being thatthe deflection coil X-X is not directly included in the anode-cathodecircuit of the driving tube and hence does not pass anode current forthe tube 32, but receives its alternating current deflection signalthrough the coupling medium of .capacitor I08.

In the operation of Figure 2, againthe damped reactive energycommunicated by the diodes I04 and I06 supplies the first portion of thedeflection cycle and in so doing stores energy on capacitor IIO therebycausing the terminal II2 to become positive with respect to the terminalII4.

This'action is identical with that described in connection with Figure 1and follows from the influence of the sum of the damping currentsthrough diodes I04 and I06 upon the capacitor "I I0, common to the loadcircuits of both damping diodes during the reaction scannin portion ofConsequently, durin the interval in which tube 32 is driven into platecurrent conduction, the elfective anode polarizing potential will be thesum of the potential available at B+ terminal I I6 and the terminalvoltage of condenser IIO resulting from the storage of reactive energy.In this way a portion of the energy extracted during the reactionscanning cycle of the deflection circuit is made available for operationof the vacuum tube 32 during the driven portion of the deflection cycleand in so doing produces the well-known B-boosting effect.

It will be appreciated that the coupling capacitor I08 serving tocommunicate deflection signal energy from the secondary of the outputtransformer I00 also serves as a D. C. blocking capacitor so that thisB-boost voltage developed across capacitor I I0 will not be in effectshort-circuited by the low D. C. resistance of the secondary windin I02.

From the operation of Figure 1, it will be discerned that theconfiguration of the present invention in effect allows a virtualtransformer step-down action without the actual utilization of astep-down transformer. This phase of the invention appears most vividlywhen considering the operation of Figure l on an average current basis.For example, after the circuitof Figure 1 has reached an equilibriumoperating condition, it is apparent that the average current throughcapacitor 64 during the drive portion of the defiection cycle (thatportion supplied by plate conduction of vacuum tube 32) is to allintents and purposes approximately twice that of the average currentpassed by each of the damping diodes 66 and I0 during the second portionor reaction scanning phase of the deflection cycle. This unique actionin itself forms an important novel and useful part of the presentinvention. Such action has here, of course, been used in connection witha television deflection damping system. It clearly follows, however,that by connecting a plurality of inductance elementsin series with oneanother with the interpositioning of a capacitance between adjacentinductances and appropriately applying a plurality of dampinginstrumentalities across suitable portions of the series combination, animpedance step-down action of practically any desired value can beobtained, In the most basic form of series damping arrangement inaccordance with the present invention, the energy recovery will manifestitself in the unidirectional potential developed across the'terminals ofthe inductance capacitance series, the potential being, of course, thesum of all the individual storage capacitors interposed between adjacentinductances. It is then only a matter of choice as to how this potentialrepresenting recovered energy is fed back into the overall system forimproving the operating efiiciency thereof. Figures 1 and 2, in thisrespect, are merely exemplary of two possible ways of advantageouslusing this recovered energy in the specific application of the inventionto television deflection systems.

What is claimed is:

1. A damped electrical system comprising in combination, a plurality ofinductance elements connected in series, at least one capacitanceelement connected in series between adjacent in ductance elements, .aplurality of damping instrumentalities connected with said series ofcapacitively connected inductances such thateach damping instrumentalityembraces a different inductance element but the same capacitanceelement, and means for exciting said series of capacitively connectedinductances with alternating voltage.

2. A damped electrical system comprising in combination, a plurality ofinductance elements connected in series, a capacitance element connectedbetween adjacent inductance elements,

a plurality of damping instrumentalities connected with said series ofcapacitively connected inductances such that at least two of saiddamping instrumentalities embrace a difierent inductance element but thesame capacitance element, and means for exciting said series ofcapacitively connected inductances with alternating voltage.

3. A damped electrical system comprising in combination, a plurality ofinductance elements connected in series to form a combination, at leastone capacitance element connected between adjacent inductance elements,a plurality of damping instrumentalities connected wih said series ofcapacitively connected inductances such that each dampinginstrumentality embraces only one inductance element and one onlycapacitance element, and means for applying alternating voltage acrossthe extremities of said inductance combination.

4. A damped electrical system comprising in combination, two inductanceelements connected in series, a capacitance element connected betweensaid inductance elements, two damping instrumentalities connected withsaid series of capacitively connected inductances such that each dampinginstrumentality embraces a separate inductance element and saidcapacitance element, and means for exciting said series of capacitivelyconnected inductances with alternating voltage.

5. An electrical damping system comprisin in combination, a source ofalternating voltage, a first and second electrical utilization meansconnected in series across said alternating voltage source, an impedanceelement, a first and second unidirectional current conducting dampingmeans respectively connected across said first and said secondutilization means, connections placing said impedance element in serieswith said first damping means such that unidirectional current flows ina given direction through said impedance element during action of saidfirst damping means, connections placin said second damping means inseries with said impedance element such that action of said seconddamping means causes unidirectional current fiow through said impedancedevice in the same given direction of current flow produced by saidfirst damping means whereby the potential appearing across saidimpedance element is a function of the additively combined dampingcurrents conducted by said first and second damping means.

6. In an electrical damping system in combination, a source ofalternating voltage, a first and second electrical utilization meansconnected in series across said alternating voltage source, a capacitor,a first and second unilaterally conductive damping devices respectivelyconnected across said first and said second utilization means,connections placing said capacitor in series with said first dampingmeans, connections placing said capacitance element also in series withsaid second damping device such that action of said second damping meanscauses said capacitor to receive charging energy in the same directionas that produced by said first damping device whereby the potentialappearing across said capacitor is a function of the additively combineddamping energy handled by said first and second damping device.

7. In an electrical damping system in combination, a first and secondinductance device each having at least two utilization terminals, animpedance element connected with one terminal of each inductance device,connections applying the other terminals of the series inductancedevices across a source of signal voltage, a first and secondunilaterally conductive damping instrumentality, connections applyingsaid first damping instrumentality across the series combination formedby said first inductance device and said impedance element, connectionsapplying said second clamping instrumentality across the seriescombination formed by said second inductance device and said impedanceelement, said damping instrumentalities being so polarized that thedamping current fiow through said impedance element due to said firstdamping instrumentality is in the same direction as the damping currentflow through said impedance element produced by said second dampinginstrumentality whereby the potential developed across said impedanceelement is a function of the additively combined damping current of saidfirst and second clamping instrumentalities.

8. In an electrical system in combination, a first and second inductancedevices, each having at least two utilization terminals, an impedanceelement connection with one terminal of each inductance device, a signalvoltage generator connection with a source of operating energy,connections applying the output of said signal generator to the otherterminals of said inductance devices, a first and second unilateralconductive damping instrumentalities, connections applying said firstdamping instrumentality across the series combination formed by saidfirst inductance device and said impedance element, connections applyingsaid second instrumentality across the series combination formed by saidfirst inductance device and said impedance element, said dampinginstrumentalities being so polarized that the damping current flowthrough said impedance element due to said first damping instrumentalityis in the same direction as the damping current flow through saidimpedance device produced by said second damping instrumentality, andconnections placing said impedance element in series with said signalgenerator and its associated source of operating energy.

9. Apparatus according to claim 8 wherein said impedance element is acapacitor of sufficient size such that a substantially constantunidirectional potential is developed across its terminals due to energycommunicated by said first and second damping instrumentalities.

10. In an electromagnetic cathode ray deflection system employing adeflection coil comprising at least two separate winding sections, saidcoil being adapted for excitation from a vacuum tube which in turnderives its operating energy from a source of unidirectional polarizingpotential, a power recovery deflection coil damping arrangementcomprising in combination, a first and second means for separatelydamping each coil winding section during one phase of the deflectioncycle, an energy storage device, connections applying said energystorage device in series with each of said damping means and also inseries with the connection of the vacuum tube with its associatedunidirectional polarizing po tential such that energy is stored in saidstorage means by said separate damping means during one portion of thedeflection cycle and made available for utilization by said vacuum tubeduring another portion of the deflection cycle.

11. In an electromagnetic cathode ray deflection system employing adeflection coil comprising at least two separate winding sections, saidcoil being adapted for excitation from a vacuum tube which in turnderives its operating energy from a source of unidirectional polarizingpotential, a power recovery deflection coil damping arrangementcomprising in combination, a first and second unilaterally conductivedamping devices each separately connected for the respective damping ofone of said deflection coil winding sections during one phase of thedeflection cycle, a capacitance, and connections including saidcapacitor in series with each of said damping devices and also in serieswith the connection of the vacuum tube and its associated unidirectionalpolarizing potential such that energy is stored in saidcapacitor by saidseparate damping devices during said one portion of the deflection cycleis made available for utilization by said vacuum tube during anotherportion of the deflection. cycle.

12. Apparatus according to claim 11, wherein a resistor'is connectedacross the terminals of said capacitor for the purpose of correcting thewaveform of the deflection signal current developed through saiddeflection coil winding sections.

13. In an electromagnetic cathode ray beam deflection system employing adeflection coil comprising at least a first and second separate windingsection, each section having a first and second utilization terminals, apower recovery damping arrangement comprising in combination, a vacuumtube having at least an anode and a cathode, said vacuum tube beingconnected for excitation from a source of deflection signal, a source ofpolarizing potential for said vacuum tube anodecathode circuit, acapacitor connected from the first terminal of the first deflection coilwinding section to the first terminal of the second deflection coilwinding section, means coupling deflection energy from said vacuum tubeanode-cathode circuit to said deflection coil winding sections, a firstunilaterally conductive damping device connected between said first coilwinding section second terminal and said second coil winding sectionfirst terminal, a second unilaterally conductive damping deviceconnected between said first coil winding section first terminal andsaid second coil winding section second terminal, and connectionsapplying the terminal voltage developed across said capacitor as theresult of the combined separate damping actions of said first and seconddamping devices in series with said source of polarizing potential andsaid vacuum tube anode-cathode circuit.

14. Apparatus according to claim 13, wherein said deflection energycoupling means comprises a step-down transformer having a primaryconnected in series with said vacuum tube anode- 10 cathode circuit anda secondary capacitively coupled to the second terminals of said firstand second coil winding sections.

15. In an electromagnetic cathode ray system employing a deflection coilcomprising at least a first and second separate winding section, eachsection having a first and second utilization terminals, a powerrecovery damping arrangement comprising in combination, a vacuum tubehaving at least an anode and a cathode said vacuum tube being connectedfor excitation from a source of deflection signal, a source ofpolarizing potential for said vacuum tube anode-cathode circuit, acapacitor connected from the first terminal of the first deflection coilwinding section to the first terminal of the second deflection coilwinding section, connections placing said first coil winding sectionsecond terminal and said second coil winding section second terminal inseries with the anode-cathode circuit, a first unilaterally conductivedamping device connected between said first coil winding section secondterminal and said second coil winding section first terminal, a secondunilaterally conductive damping device connected between said first coilwinding section first terminal and said coil winding section secondterminal whereby the effective polarizing potential for said vacuum tubeanode-cathode circuit is increased by the magnitude of the terminalvoltage developed across said capacitor as a result of the action ofsaid first and second damping devices.

16. Apparatus according to claim 15, wherein the input terminals of anautotransformer pulse step-up type power supply is also connected withsaid anode-cathode circuit of said vacuum tube for the transformation ofsome deflection signal energy to a suitable high unidirectionalpotential for application to the accelerating electrode of a cathode rayelectron tube.

ALLEN A. BARCO.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,320,551 Bahring June 1, 19432,427,263 Dodds et al Sept. 9, 1947 2,451,641 Torsch Oct. 19, 1948FOREIGN PATENTS Number Country Date 375,097 Germany May 7, 1923 868,663France Oct. 13, 1941

